A 22-year-old woman, believed to be from Britain, was taken to Westmead Hospital in a critical condition and placed in an induced coma. She was in a serious but stable condition on Sunday.

The event's organisers, Totem Onelove, took to social media to express "our deepest condolences to the friends and family of the patron who tragically passed away on Saturday night at Sydney Stereosonic".

"As it is a matter with the NSW Police and coroner we cannot make any further statements or comment," the Facebook post said.